Use of acoustic waves for purging filters in semiconductor manufacturing equipment

ABSTRACT

An apparatus and method for qualifying a filter used to filter fluid used in a coating operation associated with photolithography or other semiconductor manufacturing processes, provides a semiconductor manufacturing tool that includes a filter and an acoustic wave generator. The filter may be housed inside a filter housing and the acoustic wave generator may produce ultrasonic, megasonic or other acoustic energy. The acoustic wave generator contacts or is in close proximity with the filter housing and provides acoustic wave energy to the filter through the housing. The acoustic wave energy causes any bubbles in the filter to become disengaged.

FIELD OF THE DISCLOSURE

The disclosure is related to a method and system for using acousticwaves in the optimization of semiconductor manufacturing equipment, andmore particularly to the use of acoustic waves to purge filters used invarious coating operations associated with photolithography processesused in semiconductor manufacturing.

BACKGROUND

Photolithography is a critical and frequently used operation in themanufacture of semiconductor devices. Each semiconductor deviceundergoes multiple photolithography operations which form the patternsthat transform layers of material into interconnected circuits. Eachphotolithography operation includes an operation that coats thesubstrates with a photoresist material and a develop operation thatdevelops the exposed and patterned photoresist layer by coating thesubstrate with a developer. Photolithography operations may also utilizeadditional coating operations such as operations that coat thesubstrates with anti-reflective coatings, ARC's, adhesion promoters, andvarious other coatings. Each photolithography operation thereforeincludes multiple coating operations that dispense a photolithographyfluid onto a substrate that is rotated to produce a coating on thesubstrate surface.

The manufacturing tools that are used to coat the substrates include adispense port at which the fluid is introduced to the substrate, whichis rotated to produce a very thin coating on the substrate. It iscritical for the coating to include a thickness that is uniform and lieswithin a narrow range of acceptable thicknesses prescribed by thespecification. It is also critical to obtain the desired thickness ofthe coated material from a corresponding amount of dispensed materialbecause the fluids used in the various photolithography coatingoperations are very expensive and it would be cost prohibitive todispense excess amounts of fluid that are simply expelled from thesubstrate when it is rotated, i.e. wasted. It is also important toassure that each coating operation results in a high quality coating. Ifthere are voids in the layer coated on the substrate, if the coating isof non-uniform thickness, or if there are particles contaminating anddistorting the coated film, the substrate must be reworked atconsiderable expense. The rework procedure is also time consuming anddelays cycle time.

As such, it is critical to ensure that the fluid such as photoresist ordeveloper, that is dispensed from the dispense port is free of particlesand air bubbles and is a clean and homogeneous fluid. For this reason,each photolithography coating tool used to coat the aforementionedmaterials, advantageously includes a filter that filters the fluidbetween the fluid reservoir and the dispense port. The filters trapparticles, air bubbles and other anomalies that may be included withinthe photolithography fluid in raw form in the reservoir. The filtersmust be changed on a regular basis and the associated maintenancerequires a requalification of the filter and the fluid dispensing systembefore the tool can again be used for production runs.

The filter is, of course, porous in nature so that the fluid can passthrough the filter while any particles or other anomalies will remaintrapped in the filter. Various porous materials such as porouspolyethylene, nylon and other suitable materials may be used as theporous filter material for photoresist filters, for example. The filteris typically retained in a filter housing through which thephotolithography fluid flows. Various housing configurations areavailable and the housing may include an inlet port and an outlet portand often includes a purge port. When the photolithography fluid isfirst passed through a newly installed filter, the filter does notimmediately saturate with fluid. Rather, air bubbles are created in thefilter as small amounts of air remain trapped within the filter mediadue to the surface tension of the air bubbles adhering to the porousfilter.

The bubbles often remain in the filter for an extended time and aredifficult to remove. It is important to remove the bubbles from thefilter. Otherwise, the bubbles will become disengaged during productionoperations, and delivered to the dispense port where they cause problemssuch as voids in the coated film, when dispensed onto the substrate.Furthermore, the bubbles act as a compressible volume which affects pumpoperation, adversely affecting the coating operation.

According to one conventional technique, the photolithography fluid iscontinuously purged through the filter for an extended time until nofurther bubbles are detected in the outlet line of the filter housing.While this time-consuming qualification process is underway, the tool isnot available for production activity and considerable amounts of thephotolithography fluid are being wasted while waiting for all of thebubbles to become disengaged from the filter. The wastedphotolithography fluid represents a considerable expense, and theunavailability of the tool represents another expense.

Even during normal and continuous use, bubbles can be introduced bybeing drawn into the filter or as a result of outgassing or due tounconventional surface tension properties of the photolithography fluid.These bubbles also require purging using the same techniques asdescribed supra, and which include the same shortcomings.

The present disclosure addresses these shortcomings.

BRIEF DESCRIPTION OF THE DRAWING

The present disclosure is best understood from the following detaileddescription when read in conjunction with the accompanying drawing. Itis emphasized that, according to common practice, the various featuresof the drawing are not necessarily to scale. On the contrary, thedimensions of the various features may be arbitrarily expanded orreduced for clarity. Like numerals denote like features throughout thespecification and drawing.

FIG. 1 is a side view showing a filter housing that contains a filter;

FIG. 2 is a side view of a housing with a cut-away portion showing afilter inside the filter housing;

FIG. 3 is a side view showing bubbles formed within a filter shown in acut-away portion of a filter housing;

FIG. 4 is a perspective view of an exemplary acoustic wave generatoraccording to the invention;

FIG. 5 is a side view of a filter housing containing a filter andreceived within and contacting an acoustic wave generator according tothe invention;

FIG. 6 is another exemplary embodiment showing a filter housingcontaining a filter and contacting an acoustic wave generator accordingto the invention; and

FIG. 7 represents a photolithography coating tool including afilter/acoustic wave generator unit according to the invention.

DETAILED DESCRIPTION

The disclosure provides a method and apparatus that readies filters usedin the semiconductor manufacturing industry, for use. In particular, thedisclosure relates to filters used for filtering fluids such as liquids,gels or intermediates with various viscosities, particularly thosefluids used in photolithography operations. The photolithographyoperations include the dispensing and coating of a photolithographyfluid which may be a photoresist, a developer, an ARC (anti-reflectivecoating), various adhesion promoters, cleaning fluids or otherphotolithography fluids, i.e. fluids used for coating a substrate for aphotolithography operation.

According to other exemplary embodiments, the apparatus and method ofthe disclosure may find application in filters used in other coatingoperations, such as the coating of spin-on glass or other spin-ondielectrics also used in the semiconductor manufacturing industry. Theapparatus and method of the disclosure may find application in anyfilter used to filter fluids.

The disclosure provides a dispensing and coating apparatus thatdispenses a fluid onto a substrate and rotates the substrate, such thatthe dispensed fluid becomes a thin coating spread across the substrate.The substrate may be a semiconductor wafer used in the semiconductorfabrication industry, in one exemplary embodiment. The apparatusdispenses the fluid at a dispense port and fluid is delivered to thedispense port through various delivery systems and lines within theapparatus. The fluid is filtered before it reaches the dispense port bya filter disposed within a filter housing and included within thedispensing/coating apparatus, although, in other exemplary embodiments,the filter and filter housing may be remote from the dispensing/coatingapparatus. The apparatus further includes a fluid source, which may be abottle or other reservoir, and a pump that pumps the fluid through thefilter and to the dispense port. Many such coating apparatuses are knownin the art and are not described further herein.

FIG. 1 shows an exemplary configuration of a filter housing thatcontains a filter for a photolithography fluid. Filter housing 2includes ports 4 and flange 8 which may be useful in installing filterhousing 2 in a designated location within a photolithography dispensingand coating apparatus. This configuration is exemplary only and in otherexemplary embodiments, filter housing 2 may take on completely differentconfigurations. Ports 4 are three in number and this is exemplary aswell. In one exemplary embodiment, ports 4 may include an inlet port, anoutlet port, and a separate port for purging. Filter housing material 10may be Teflon or other suitable materials such as HDPE, high-densitypolyethylene, but other suitable materials may be used in otherexemplary embodiments and depending upon the fluid being filtered in thefilter housing.

FIG. 2 shows filter housing 2 with cutaway 12 exposing the interior offilter housing 2 and showing filter 14 contained within filter housing2. Filter 14 is a porous filter material that may be formed of varioussuitable materials compatible with materials used in the semiconductormanufacturing industry. Filter 14 includes a microstructure that trapsparticles and may also trap bubbles, and provides its porosity.According to one exemplary embodiment, the filter may be formed ofnylon, such as nylon 6, 6 (N₆₆) and according to other exemplaryembodiments, the filter may be formed of polytetrafluoroethylene (Teflonor PTFE), high-density polyethylene (HDPE) ultra high molecular weightpolyethylene (UHMWPE) or other suitable materials dictated byapplication. In one exemplary embodiment, filter 14 may be a photoresistfilter and many photoresist filters are commercially available.According to another exemplary embodiment, filter 14 may be a developerfilter. Many developer filters are commercially available.

After filter 14 has been in use for an amount of time, it will bereplaced by a new filter. This is typically done by replacing theintegrated unit of filter housing 2 that contains filter 14. When thenew filter housing 2 unit is installed, fluid must be cycled throughfilter 14 until the fluid emanating from the filter housing is acontinuous substantially homogenous fluid free of particles and bubbles.

FIG. 3 shows another cutaway view of filter 14 within filter housing 2and shows a number of bubbles 18 retained within filter 14. This mayrepresent the situation after a filter has been replaced by a newlyinstalled filter and fluid is run through the filter, such as byentering through one port 4 and exiting through another port 4 or it mayrepresent the situation whereby bubbles are created during continuousoperation. The number and size of bubbles varies according to variousexemplary embodiments and is determined in part by the nature andporosity of filter 14 and the viscosity of the particular fluid beingfiltered. When a new filter 14 is installed, and fluid is introducedinto filter 14, the filter does not immediately saturate with fluid.Rather, small amounts of air remain trapped within the media due to thesurface tension of the air bubbles adhering to the microstructure offilter 14. According to conventional techniques, a considerable volumeof fluid must be run through a newly installed filter 14 or through anyfilter 14 replete with bubbles, in order to eventually dislodge bubbles18.

FIG. 4 is a perspective view showing an acoustic wave generatoraccording to the disclosure. Acoustic wave generator 20 may be capableof generating ultrasonic energy, typically sound waves having afrequency of about 20-400 kHz and in one embodiment, about 100 kHz.According to another exemplary embodiment, acoustic wave generator 20may generate megasonic energy, i.e. sound waves having a higherfrequency that may range from 800-2000 kHz. In other exemplaryembodiments, other high frequency sound waves may be used. Acoustic wavegenerator 20 is coupled to a power source through cord 22 and mayinclude various suitable and known elements for generating and directingacoustic wave energy. Various suitable acoustic wave generating elementssuch as a piezoelectric crystal transducer, or other acoustic wavegenerating elements may be used. A commonly used piezo material is PZTceramic, lead zirconate titanate. Barium titanate is another suitablepiezo ceramic that may be used.

Acoustic wave generator 20 may be capable of producing multiple forms ofacoustic energy, i.e. sound waves having frequencies that may vary andextend from the ultrasonic range to the megasonic range. Acoustic wavegenerator 20 may be operable to produce acoustic waves of multiplefrequencies at different spatial locations and the waves may be directedin different directions. Acoustic wave generator 20 includes recess 24and inner sidewalls 28 and base 30 for conterminously and detachablyreceiving a filter housing in recess 24. According to another exemplaryembodiment, the filter housing may be received within opening 24 in asnug manner or a loose manner. Because the filter housing is receivedwithin opening 24 in a loose manner, it is easily detachable fromacoustic wave generator 20. According to the various exemplaryembodiments, acoustic wave generator 20 is capable of generatingacoustic wave energy and directing it to filter 14 disposed withinfilter housing 2.

According to one exemplary embodiment, acoustic wave generator 20 may beannular in shape and may include energy zones such as zones 26A-26J atdifferent spatial locations as illustrated. According to one exemplaryembodiment, zones 26A-26J may be separately operable such that differentzones may be operated at different times. According to one exemplaryembodiment, zones 26A-26J may be sequentially powered on and off,thereby sequentially generating acoustic energy waves and sequentiallydirecting the energy waves to the filter within filter housing 2. Zones26A-26J thereby direct acoustic wave energy to a filter disposed withina housing received in opening 24, from different directions.

Each zone 26A-26J may include an individual separately operabletransducer element capable of generating acoustic waves. According toone exemplary embodiment, zones 26A-26J may produce waves of differentfrequencies and in some exemplary embodiment, each zone 26A-26J may becapable of generating multiple wavelengths of acoustic waves. Varioussuitable acoustic wave generating elements such as piezoelectriccrystals, or other acoustic wave generating transducers may be used.

Various controllers may be used to control acoustic wave generator 20 toproduce to various effects described herein and, in particular, toseparately control respective zones 26A-26J. The controller such ascontroller 25 of FIG. 4, may be programmable so as to control acousticwave generator 20 using various recipes for the generation and deliveryof the various acoustic waves.

It should be understood that the configurations shown in FIG. 4 isexemplary only. Other configurations for acoustic wave generator 20 maybe utilized in other exemplary embodiments and may be designed inconjunction with the shape of the filter housing used in a particularcoating apparatus.

FIG. 5 shows filter housing 2 received within exemplary acoustic wavegenerator 20 shown in FIG. 4. Filter housing 2 may be received withinopening 24 of acoustic wave generator such that inner sidewalls 28 ofopening 24 circumferentially contact the outer surfaces of filterhousing 2. According to one exemplary embodiment, and referring to FIG.4, a gel may be spread along inner sidewalls 28 or filter housing 2 orboth, such that the gel is disposed at the interface between a surfaceof acoustic wave generator 20 and a surface of filter housing 2 whenthey are in contact. A portion of gel 29 is shown in FIG. 4. The gel maybe sorbothane or any gel that provides good contact such as otherelastic polymers or visco-elastic materials.

FIG. 6 shows another exemplary configuration of acoustic wave generator20. According to the illustrated embodiment in FIG. 6, filter housing 2such as illustrated in previous figures, is received within asemicircular recess formed within acoustic wave generator 20. In thisexemplary embodiment, a different contact area is provided betweenacoustic wave generator 20 and filter housing 2. Although acoustic wavegenerator 20 does not completely circumferentially surround filterhousing 2, acoustic wave generator 20 contacts filter housing 2 atvertical locations up to flange 8.

FIGS. 5 and 6 are intended to be exemplary only and in other exemplaryembodiments, acoustic wave generator 20 and filter housing 2 may eachtake on different configurations. In other exemplary embodiments,acoustic wave generator 20 may be itself reconfigurable to accommodatedifferently shaped and sized filter housings and different installationconfigurations. An aspect of the disclosure is that filter housing 2 isin suitably close proximity to acoustic wave generator 20 such thatacoustic wave generator 20 directs acoustic wave energy into filter 14disposed within filter housing 2. In some exemplary embodiments, filterhousing 2 and acoustic wave generator 20 may be in close proximity. Inother exemplary embodiments, filter housing 2 and acoustic wavegenerator 20 may be in contact and in other exemplary embodiments,filter housing 2 may be partially or completely received within anopening or other recess formed in acoustic wave generator 20.

The acoustic wave energy in the form of an ultrasonic, megasonic orother high frequency acoustic wave, causes the disengagement of anybubbles that may be present in filter 14, such as may be generatedduring continuous normal operation or such as may be present after a newfilter is installed and the fluid has been introduced to the filter andcycled through the filter to qualify the filter for production use. Inthis manner, bubbles are quickly removed from filter 14 and the filteris quickly qualified for production use. According to various exemplaryembodiments, detectors that detect bubbles in a fluid line may becoupled to the outlet fluid line from the filter housing and the time atwhich the newly installed filter is free of bubbles, may beautomatically detected.

According to one aspect, provided is an apparatus comprising a porousfilter media disposed within a housing and an acoustic wave generatorcontacting the housing and capable of applying acoustic energy to theporous filter media.

According to another aspect, provided is a photolithography coatingapparatus. The apparatus comprises a dispense station including a chuckfor receiving a substrate thereon, a dispense port positioned todispense a photolithography fluid to a substrate on the chuck, a sourceof the photolithography fluid, a filter for filtering thephotolithography fluid, the filter comprising a porous filter mediawithin a housing, and an acoustic wave generator contacting the housingand capable of applying acoustic energy to the porous filter media.

FIG. 7 is a labeled representation of an exemplary photolithographycrating apparatus 40 including dispense/coat station 42, filter/acousticwave generator unit 44 and pump 46, as components therein, according tovarious exemplary embodiments. Dispense/coat station 42 includes chuck43 for receiving a substrate thereon.

Another aspect of the disclosure is a method for preparing a filter foruse in a fluid dispensing system. The method comprises providing aporous filter in a housing, the housing comprising an inlet port and anoutlet port coupled to a dispense line and directing acoustic waves tothe porous filter using an acoustic wave generator that contacts thehousing.

The preceding merely illustrates the principles of the disclosure. Itwill thus be appreciated that those skilled in the art will be able todevise various arrangements which, although not explicitly described orshown herein, embody the principles of the disclosure and are includedwithin its spirit and scope. Furthermore, all examples and conditionallanguage recited herein are principally intended expressly to be onlyfor pedagogical purposes and to aid the reader in understanding theprinciples of the disclosure and the concepts contributed by theinventors to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the disclosure, as well as specific examples thereof, areintended to encompass both structural and functional equivalentsthereof. Additionally, it is intended that such equivalents include bothcurrently known equivalents and equivalents developed in the future,i.e., any elements developed that perform the same function, regardlessof structure.

This description of the exemplary embodiments is intended to be read inconnection with the figures of the accompanying drawing, which are to beconsidered part of the entire written description. In the description,relative terms such as lower, upper, horizontal, vertical, above, below,up, down, top and bottom as well as derivatives thereof (e.g.,horizontally, downwardly, upwardly, etc.) should be construed to referto the orientation as then described or as shown in the drawing underdiscussion. These relative terms are for convenience of description anddo not require that the apparatus be constructed or operated in aparticular orientation. Terms concerning attachments, coupling and thelike, such as “connected” and “interconnected,” refer to a relationshipwherein structures are secured or attached to one another eitherdirectly or indirectly through intervening structures.

Although the disclosure has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodimentsof the disclosure, which may be made by those skilled in the art withoutdeparting from the scope and range of equivalents of the disclosure.

What is claimed is:
 1. A photolithography coating apparatus comprising:a dispense station including a chuck for receiving a substrate thereon;a dispense port positioned to dispense a photolithography fluid onto asubstrate on said chuck; a source of said photolithography fluid; afilter for filtering said photolithography fluid, said filter comprisinga porous filter media within a housing having an inlet port and anoutlet port; and an acoustic wave generator that applies acoustic energyto said porous filter media, said acoustic wave generator including abase with a recessed portion wherein said recessed portion is a cavityin an exterior surface of said base and said recessed portion receivessaid housing therein and side portions of said recessed portion of saidbase conterminously surround said housing.
 2. The photolithographycoating apparatus as in claim 1, wherein said acoustic energy comprisesone of ultrasonic energy and megasonic energy.
 3. The photolithographycoating apparatus as in claim 1, wherein said photolithography fluidcomprises photoresist and said porous filter media comprises aphotoresist filter.
 4. The photolithography coating apparatus as inclaim 1, wherein said photolithography fluid comprises developer, saidporous filter media comprises a developer filter and further comprisinga gel disposed at an interface between said acoustic wave generator andsaid housing.
 5. The photolithography coating apparatus as in claim 1,further comprising a pump that pumps said photolithography fluid throughsaid porous filter media and to said dispense port.
 6. Thephotolithography coating apparatus as in claim 1, wherein said acousticwave generator includes a controller that generates and applies saidacoustic energy with different frequencies, in different directions andat different spatial locations.
 7. The photolithography coatingapparatus as in claim 1, wherein said acoustic wave generator includes aplurality of separately operable zones.
 8. A photolithography coatingapparatus comprising: a dispense station including a chuck for receivinga substrate thereon; a dispense port positioned to dispense aphotolithography fluid onto a substrate on said chuck; a source of saidphotolithography fluid; a filter for filtering said photolithographyfluid, said filter comprising a porous filter media within a housing;and an acoustic wave generator that applies acoustic energy to saidporous filter media, said acoustic wave generator including a base witha recessed portion wherein said recessed portion is a cavity in anexterior surface of said base' said recessed portion receives saidhousing therein and side portions of said recessed portion of said baseconterminously surround said housing.
 9. The photolithography coatingapparatus as in claim 8, wherein said acoustic wave generator includes acontroller that generates and applies said acoustic energy withdifferent frequencies, in different directions and at different spatiallocations.
 10. The photolithography coating apparatus as in claim 8,wherein said acoustic wave generator detachably receives said housingtherein.
 11. The photolithography coating apparatus as in claim 10,further comprising a gel disposed at an interface between said acousticwave generator and said housing.
 12. The photolithography coatingapparatus as in claim 10, wherein said acoustic wave generator includesa controller that generates and applies said acoustic energy withdifferent frequencies, in different directions and at different spatiallocations.
 13. The photolithography coating apparatus as in claim 8,wherein said acoustic wave generator includes a plurality of separatelyoperable zones.
 14. The photolithography coating apparatus as in claim13, wherein said acoustic wave generator detachably receives saidhousing therein.
 15. The photolithography coating apparatus as in claim1, wherein said inlet port and said outlet port are on the same side ofsaid housing.
 16. The photolithography coating apparatus as in claim 8,wherein said cavity has a circular shape and said side portions comprisea continuous sidewall that circularly surrounds said recessed portion byextending around a circumference of said circular shape.
 17. Thephotolithography coating apparatus as in claim 8, wherein said recessedportion includes a circular recessed surface recessed with respect tosaid exterior surface of said base.